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Here, we developed magnetically recoverable biocatalysts based on magnetite nanoparticles coated with an ultra-thin layer (about 0.9 nm) of chitosan (CS) ionically cross-linked by sodium tripolyphosphate (TPP). Excessive CS amounts were removed by multiple washings combined with magnetic separation. Glucose oxidase (GOx) was attached to the magnetic support via the interaction with N-hydroxysuccinimide (NHS) in the presence of carbodiimide (EDC) leading to a covalent amide bond. These steps result in the formation of the biocatalyst for D-glucose oxidation to D-gluconic acid to be used in the preparation of pharmaceuticals due to the benign character of the biocatalyst components. To choose the catalyst with the best catalytic performance, the amounts of CS, TPP, NHS, EDC, and GOx were varied. The optimal biocatalyst allowed for 100% relative catalytic activity. The immobilization of GOx and the magnetic character of the support prevents GOx and biocatalyst loss and allows for repeated use. [ABSTRACT FROM AUTHOR]

This work is devoted to the investigation of the possibility of the use of Ru-containing catalysts on the basis of polymeric matrix of hypercrosslinked polystyrene (HPS) in the hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL). HPS-based Ru-containing catalysts were synthesized at variation of HPS type (MN100 bearing amino groups or MN270 without functional groups) and metal content. Catalyst 5%-Ru/MN100 was shown to compete with commercial 5%-Ru/C and to allow carrying out the hydrogenation of LA in aqueous medium with high yields of GVL (more than 99%).

Biocatalysts based on magnetically responsive supports and the immobilized enzyme - cellulase- demonstrated the high activity in the carboxymethylcellulose (CMC) hydrolysis. Magnetic supports were obtained by two ways: (i) the synthesis of magnetite nanoparticles (NPs) followed by silica shell coating, (ii) the form magnetite NPs by crystallization ones in the pores of mesoporous silica. Physico-chemical methods (low-temperature nitrogen adsorption, scanning electron microscopy, electron-transparent specimens for transmission electron microscopy and magnetic measurements) were utilized for characterization of the structure and surface of the obtained magnetic support. The loading of the enzyme on magnetic supports of both types was approximately the same and amounted to 75-78 %. Cellulase immobilized on magnetic mesoporous silica (SiO2@Fe3O4@CEL) showed 87 % activity of the free enzyme. The scientific novelty of this work is that the controlled pore size in the mesopore range allows bulky enzyme molecules to be immobilized. The large surface area improves catalytic efficiency by increasing enzyme loading and finely dispersing biocatalyst molecules. The limiting effect of mesopores can improve the stability of the enzyme and its resistance to extreme pH and temperature. However, the use of immobilized cellulase may be limited due to the efficiency of the regeneration process. As a solution to this problem, the use of magnetic nanoparticles incorporated into a mesoporous silica matrix is proposed. The magnetic nanobiocatalyst can be easily removed from the reaction mixture using an external magnet. [ABSTRACT FROM AUTHOR]

A cascade reaction is defined as the chemical process which consists of two or more consecutive reactions carried out in the same reaction vessel due to the multifunctionality of the catalyst. This approach was utilized by researchers to design advanced biocatalysts with two or more enzymes immobilized on the same support. The key benefits of multienzyme biocatalysts rise from a single pot, where consecutive reactions are performed, thus eradicating the handling of intermediate products. This makes processes more sustainable, allowing one to obtain target molecules in a more environmentally friendly way. We report on the effect of pore size in biocatalysts based on mesoporous silica on the loading of immobilized enzymes glucose oxidase (GOx) and horseradish peroxidase (HRP) as well as on the activity and the possibility of reuse of the bio-enzyme biocatalyst in a cascade reaction. The choice of silica substrates was due to their commercial availability and sharply different pore sizes: 6 nm and 15 nm. In the first case, the pores are too small to accommodate GOx and HRP, the hydrodynamic diameter of which is ~ 8 nm for each, while in the second case, there is enough space for immobilization of GOx and HRP inside the pores. We demonstrate that larger pores provide higher enzyme throughput due to immobilization within the pores, remarkable 95% relative activity, and increased stability during reuse due to the conformational integrity of GOx and HRP in spacious pores. This study clearly shows the advantages of substrates with pores larger than the size of the enzyme for its immobilization during the synthesis of the biocatalyst. [ABSTRACT FROM AUTHOR]